New cycloadditions developed in our laboratories will be investigated as means to synthesize azulenes and hydroazulenes (of potential importance as anti-tumor agents), cyclopentapyridazines (analogs of known anti-neoplastic agents which act as DNA metabolites), medium ring heterocyclic compounds (analogous to clinical antihypertensives), a variety of heterocycles substituted by novel groups such as the phosphonate and ammonium moieties (analogs to the antibiotic phosphonomycin and antitubercular and antibacterial cycloserine), and tricyclic aromatic compounds (analogs of major tranquilizers). These studies have the quadruple purpose of; (1) providng new syntheses of known chemotherapeutic agents, (2) developing novel, but general, synthetic methods based on cycloaddition, (3) production of analogs of clinically useful drugs, and (4) verifying and refining a theoretical method of predicting new cycloaditions and the regioselectivity, stereoselectivity and reactivity in synthetically valuable cycloadditions such as the Diels-Alder reaction and 1,3-dipolar cycloadditions.